[sw/silicon_creator] Add structured kChipInfo to ROM

This commit adds a new `chip_info_t` struct that contains info about the
ROM's provenance. The ROM now prints the Git commit hash on shutdown
after the "VER:" prefix.

The ROM linker script was already configured to place the .chip_info
section at the top of ROM, but I'm not confident that it worked as
expected. The autogenerated header contained a static constant, so I
think a copy would be inlined at some arbitrary location into any
compilation unit that used it, rather than being placed by the linker
script.

To verify that the ROM prints the Git commit hash on shutdown:

    ./bazelisk.sh test --test_output=streamed \
      //sw/device/silicon_creator/rom/e2e:shutdown_output_dev_fpga_cw310_rom

To verify that the .chip_info section contains data from chip_info.o:

    ./bazelisk.sh build-then 'less %s' --config riscv32 \
      //sw/device/silicon_creator/rom:rom_with_fake_keys_fpga_cw310_map

To see the value of `kChipInfo` at the end of ROM:

    ./bazelisk.sh build-then 'xxd %s | less' --config riscv32 \
      //sw/device/silicon_creator/rom:rom_with_fake_keys_fpga_cw310_bin

For example, here's the end of the ROM from the previous command. At
0x7f80, there are 64 bits of a Git commit hash (e20871e1cf102bf6).

    00007f70: 0000 0000 0000 0000 0000 0000 0000 0000  ................
    00007f80: f62b 10cf e171 08e2                      .+...q..

Issue #14892
Signed-off-by: Dan McArdle <dmcardle@opentitan.org>

rules/autogen.bzl

@@ -65,35 +65,34 @@ autogen_hjson_header = rule(
     },
 )
 
-def _chip_info(ctx):
-    header = ctx.actions.declare_file("chip_info.h")
+def _chip_info_src(ctx):
+    out_source = ctx.actions.declare_file("chip_info.c")
     ctx.actions.run(
-        outputs = [header],
+        outputs = [
+            out_source,
+        ],
         inputs = [
             ctx.file.version,
             ctx.executable._tool,
         ],
         arguments = [
             "-o",
-            header.dirname,
+            out_source.dirname,
             "--ot_version_file",
             ctx.file.version.path,
         ],
         executable = ctx.executable._tool,
     )
+
     return [
-        CcInfo(compilation_context = cc_common.create_compilation_context(
-            includes = depset([header.dirname]),
-            headers = depset([header]),
-        )),
-        DefaultInfo(files = depset([header])),
+        DefaultInfo(files = depset([out_source])),
     ]
 
-autogen_chip_info = rule(
-    implementation = _chip_info,
+autogen_chip_info_src = rule(
+    implementation = _chip_info_src,
     attrs = {
         "version": attr.label(
-            default = "//util:ot_version_file",
+            default = "//util:scm_revision_file",
             allow_single_file = True,
         ),
         "_tool": attr.label(
@@ -104,6 +103,26 @@ autogen_chip_info = rule(
     },
 )
 
+def autogen_chip_info(name):
+    """Generates a cc_library named `name` that defines chip info."""
+
+    # Generate a C source file that defines the chip info struct. This is an
+    # implementation detail and should not be depended on externally.
+    chip_info_src_target = name + "_gen_src"
+    autogen_chip_info_src(name = chip_info_src_target)
+
+    # Package up the generated source file with its corresponding header file
+    # and dependencies. Any target that wants access to the chip info should
+    # depend on this.
+    native.cc_library(
+        name = name,
+        srcs = [chip_info_src_target],
+        hdrs = ["//sw/device/silicon_creator/lib:chip_info.h"],
+        deps = [
+            "//sw/device/lib/base:macros",
+        ],
+    )
+
 def _cryptotest_hjson_external(ctx):
     """
     Implementation of the Bazel rule for parsing externally-sourced test vectors.

sw/device/lib/testing/test_rom/BUILD

@@ -5,16 +5,11 @@
 load("//rules:opentitan.bzl", "OPENTITAN_CPU", "opentitan_rom_binary")
 load("//rules:opentitan_test.bzl", "opentitan_functest")
 load("//rules:exclude_files.bzl", "exclude_files")
-load("//rules:autogen.bzl", "autogen_chip_info")
 load("//rules:linker.bzl", "ld_library")
 load("@rules_pkg//pkg:mappings.bzl", "pkg_files")
 
 package(default_visibility = ["//visibility:public"])
 
-autogen_chip_info(
-    name = "chip_info",
-)
-
 ld_library(
     name = "linker_script",
     script = "test_rom.ld",
@@ -120,7 +115,6 @@ cc_library(
     ],
     target_compatible_with = [OPENTITAN_CPU],
     deps = [
-        ":chip_info",
         ":target_test_rom_lib",
         ":test_rom_manifest",
         "//hw/ip/csrng/data:csrng_regs",
@@ -153,6 +147,7 @@ cc_library(
         "//sw/device/lib/testing:pinmux_testutils",
         "//sw/device/lib/testing/test_framework:check",
         "//sw/device/lib/testing/test_framework:status",
+        "//sw/device/silicon_creator/lib:chip_info",
         "//sw/device/silicon_creator/lib/base:sec_mmio",
         "//sw/device/silicon_creator/lib/base:static_critical_boot_measurements",
         "//sw/device/silicon_creator/lib/base:static_critical_epmp_state",

sw/device/lib/testing/test_rom/test_rom.c

@@ -22,8 +22,8 @@
 #include "sw/device/lib/testing/pinmux_testutils.h"
 #include "sw/device/lib/testing/test_framework/check.h"
 #include "sw/device/lib/testing/test_framework/status.h"
-#include "sw/device/lib/testing/test_rom/chip_info.h"  // Generated.
 #include "sw/device/silicon_creator/lib/base/sec_mmio.h"
+#include "sw/device/silicon_creator/lib/chip_info.h"
 #include "sw/device/silicon_creator/lib/drivers/flash_ctrl.h"
 #include "sw/device/silicon_creator/lib/drivers/retention_sram.h"
 #include "sw/device/silicon_creator/lib/manifest.h"
@@ -152,7 +152,7 @@ bool rom_test_main(void) {
   }
 
   // Print the chip version information
-  LOG_INFO("%s", chip_info);
+  LOG_INFO("kChipInfo: scm_revision=%x", kChipInfo.scm_revision);
 
   // Skip sram_init for test_rom
   dif_rstmgr_reset_info_bitfield_t reset_reasons;

sw/device/silicon_creator/lib/BUILD

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 load("//rules:opentitan.bzl", "OPENTITAN_CPU")
+load("//rules:autogen.bzl", "autogen_chip_info")
 load("//rules:opentitan_test.bzl", "cw310_params", "opentitan_functest", "verilator_params")
 load("//rules:cross_platform.bzl", "dual_cc_device_library_of", "dual_cc_library", "dual_inputs")
 
@@ -272,6 +273,8 @@ filegroup(
     ],
 )
 
+autogen_chip_info(name = "chip_info")
+
 dual_cc_library(
     name = "shutdown",
     srcs = dual_inputs(
@@ -289,6 +292,7 @@ dual_cc_library(
             "@googletest//:gtest",
         ],
         shared = [
+            ":chip_info",
             ":error",
             ":epmp_defs",
             "//sw/device/lib/base:hardened",

sw/device/silicon_creator/lib/chip_info.h

@@ -0,0 +1,27 @@
+// Copyright lowRISC contributors.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_
+#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_
+
+#include <stdint.h>
+
+#include "sw/device/lib/base/macros.h"
+
+typedef struct chip_info {
+  // A truncated commit hash from the open-source OpenTitan repo that can be
+  // used to reproduce the ROM binary.
+  uint64_t scm_revision;
+} chip_info_t;
+
+// This struct contains information about the ROM's provenance, and critically,
+// it can be manually decoded from a hexdump. The linker script should place
+// this at the top of the ROM.
+extern const chip_info_t kChipInfo __attribute__((section(".chip_info")));
+
+// Track the size of `kChipInfo` so we can compute how much space is left in the
+// `.chip_info` section. If it becomes too large, linking will fail.
+OT_ASSERT_SIZE(chip_info_t, 8);
+
+#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_

sw/device/silicon_creator/lib/shutdown.c

@@ -15,6 +15,7 @@
 #include "sw/device/lib/base/memory.h"
 #include "sw/device/lib/base/multibits.h"
 #include "sw/device/lib/base/stdasm.h"
+#include "sw/device/silicon_creator/lib/chip_info.h"
 #include "sw/device/silicon_creator/lib/drivers/alert.h"
 #include "sw/device/silicon_creator/lib/drivers/lifecycle.h"
 #include "sw/device/silicon_creator/lib/drivers/otp.h"
@@ -379,14 +380,19 @@ SHUTDOWN_FUNC(NO_MODIFIERS, shutdown_report_error(rom_error_t reason)) {
   uart_ctrl_reg = bitfield_bit32_write(uart_ctrl_reg, UART_CTRL_TX_BIT, true);
   abs_mmio_write32(kUartBase + UART_CTRL_REG_OFFSET, uart_ctrl_reg);
 
+  // Extract the commit hash from the `chip_info` at the top of ROM.
+  uint64_t chip_info_version = kChipInfo.scm_revision;
+  uint32_t chip_info_version_truncated = chip_info_version >> 32;
+
   // Print the error message and the raw life cycle state as reported by the
   // hardware.
   shutdown_print(kShutdownLogPrefixBootFault, redacted_error);
   shutdown_print(kShutdownLogPrefixLifecycle, raw_state);
+  shutdown_print(kShutdownLogPrefixVersion, chip_info_version_truncated);
 
 #ifdef OT_PLATFORM_RV32
   // Wait until UART TX is complete.
-  static_assert(2 * kErrorMsgLen <= kUartFifoSize,
+  static_assert(3 * kErrorMsgLen <= kUartFifoSize,
                 "Total message length must be less than TX FIFO size.");
   CSR_WRITE(CSR_REG_MCYCLE, 0);
   uint32_t mcycle;

sw/device/silicon_creator/lib/shutdown.h

@@ -87,6 +87,7 @@ typedef enum shutdown_error_redact {
 typedef enum shutdown_log_prefix {
   kShutdownLogPrefixBootFault = LOG_PREFIX_('B', 'F', 'V'),
   kShutdownLogPrefixLifecycle = LOG_PREFIX_('L', 'C', 'V'),
+  kShutdownLogPrefixVersion = LOG_PREFIX_('V', 'E', 'R'),
 } shutdown_log_prefix_t;
 
 /**

util/BUILD

@@ -23,6 +23,13 @@ genrule(
     stamp = 1,  # this provides volatile-status.txt
 )
 
+genrule(
+    name = "scm_revision_file",
+    outs = ["scm_revision.txt"],
+    cmd = """awk '/BUILD_SCM_REVISION/ { print $$2 }' bazel-out/volatile-status.txt > $@""",
+    stamp = 1,  # this provides volatile-status.txt
+)
+
 py_binary(
     name = "otbn_build",
     srcs = ["otbn_build.py"],

util/rom_chip_info.py

@@ -6,26 +6,39 @@
 """
 
 import argparse
+import hashlib
 import logging as log
 import sys
-from datetime import datetime
 from pathlib import Path
 
-header_template = r"""
+
+def generate_chip_info_c_source(scm_revision: int) -> str:
+    """Return the contents of a C source file that defines `kChipInfo`.
+
+    Args:
+        scm_revision: SHA1 sum identifying the current SCM revision.
+    """
+
+    SHA1_DIGEST_SIZE_BITS = hashlib.sha1().digest_size * 8
+    assert scm_revision.bit_length() <= SHA1_DIGEST_SIZE_BITS
+
+    # Truncate the SCM revision to the top N bits.
+    SCM_REVISION_SIZE_BITS = 64
+    shift_amount = SHA1_DIGEST_SIZE_BITS - SCM_REVISION_SIZE_BITS
+    scm_revision >>= shift_amount
+
+    return f"""
 // Copyright lowRISC contributors.
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0
 //
 // --------- W A R N I N G: A U T O - G E N E R A T E D   C O D E !! ---------//
 
-#ifndef _F_CHIPINFO_H__
-#define _F_CHIPINFO_H__
-
-static const char chip_info[128] __attribute__((section(".chip_info"))) =
-  "Version: {%version%}, Build Date: {%build_date%}";
-
-#endif  // _F_CHIPINFO_H__
+#include "sw/device/silicon_creator/lib/chip_info.h"
 
+const chip_info_t kChipInfo __attribute__((section(".chip_info"))) = {{
+    .scm_revision = (uint64_t){scm_revision:#0x},
+}};
 """
 
 
@@ -57,24 +70,18 @@ def main():
         log.error(
             "Missing ot_version, provide --ot_version or --ot_version_file.")
         raise SystemExit(sys.exc_info()[1])
+    version = int(version, base=16)
+    log.info("Version: %x" % (version, ))
 
     outdir = Path(args.outdir)
 
     outdir.mkdir(parents=True, exist_ok=True)
-    out_path = outdir / "chip_info.h"
-
-    now = datetime.now()
-    wall_time = now.strftime("%Y-%m-%d %H:%M:%S")
-
-    log.info("Version: %s" % (version, ))
-    log.info("Build Date: %s" % (wall_time, ))
+    source_out_path = outdir / "chip_info.c"
 
-    output = header_template
-    output = output.replace('{%version%}', version, 1)
-    output = output.replace('{%build_date%}', wall_time, 1)
+    output = generate_chip_info_c_source(version)
 
-    with out_path.open(mode='w', encoding='UTF-8') as fout:
-        fout.write(output + "\n")
+    with source_out_path.open(mode='w', encoding='UTF-8') as fout:
+        fout.write(output)
 
 
 if __name__ == "__main__":